Digital computers have evolved to include various different user interface devices that enable a user to steer a cursor around a screen to select among displayed menus and other objects and to perform various other functions. A computer mouse is one widely used type of user interface device. The mouse is usually connected by cable to the computer, but may instead be connected via a wireless interface. The mouse may use a roller ball or a light source (e.g., LED) coupled to a light sensor to sense movement of the mouse. Movement of the mouse is interpreted by the computer as, for example, a user command to move a cursor on the screen. The mouse generally includes several buttons that can be actuated by a user to, for example, signal the user's selection of a displayed menu or other object that is adjacent to the cursor.
In portable computer applications the mouse has the drawback of being separate from the computer. Accordingly, the user can be inconvenienced by the need to remember to bring along the mouse when traveling with or otherwise moving the computer, and by the need to separately pack both the computer and mouse. This inconvenience has prompted the evolution of other user interface devices that are integral to the computer, such as a touchpad disposed in the computer housing and a joystick associated with the computer keyboard.